Electromagnetic apparatus for controlling beams of light



April 1940- J. EGGERT m- AL 2,197,466

' ELECTROMAGNETIC APPARATUS FOR CONTROLLING BEAMS OF LIGHT Filed Nov. 5, 1937 2 Sheets-Sheet 1 John E gger Hams Fm'edm'c/z /Vlssen Inventors By Their Azfomeys April 1940- J. EGGERT ET AL 2,197,456

ELECTROMAGNETIC APPARATUS FOR CONTROLLING BEAMS OF LIGHT Filed Nov. 5, 1937 2 Sheets-Sheet 2 22 7 23 J hn 'ggert V Hans Friedrich Nz'uen Inventors By Their Afforneys Patented Apr. 16, 1940 UNITED. STATES PATENT OFFICE John Est Lelii l, and Hans Friedrich Nkaen, Decca a-ignors to I. G. Farben:

indnstrie Aktiengeeellachait,

the-Main, Germany Application November 5,1937, Serial No. I72)" In Germany November 7, 1836 Claims.

Our present invention relates to an apparatus for controlling beams of light.

One of its objects is to provide an apparatus for controlling a beam of light by means of a l two-pole electro-magnetic controlling system and a permanently magnetized oscillating device.

' Further-objects of this invention will be understood irom the following detailed description of the same.

are known which consist in a magnet having on its ends coils through which the controlling currents flow, whereby a permanent magnetic field is augmented or diminished. This determines the application of a varying force 'to an armature which can be used to control the light beam. Further apparatus are known in which a coil is mounted on an iron core one end of which is ar ranged in the middle 01' a magnet and the other 39 end is close to a movable mirror support which is near the two poles of the magnet. In all these apparatus,=however,' the magnetic circuit of the alternating magnetic field flows through the steel magnet." This is a disadvantage, since the steel has irreversible, small permeability and oflers a. high resistance to variations in magnetization. Furthermore eddy currents are set up.

These disadvantages are minimized or avoided by the present invention, wherein the oscillating device is arranged in such a manner that the circuit for the magnetic flux. due to the electromagnet iscompleted only through the oscillating device. The latter may advantageously consist of two parts placed respectively opposite to the a two poles oi the electromagnet, so that when the controlling currents flow through the field coils one part is attracted and the other repelled. The

- parts or the oscillating device mayhave the form "of tongues, one end of each being fixed to the 49 permanent magnet, the other ends are placed respectively opposite to the two poles of the electromagnet. The resonant frequency of the tongues depends mainly on their-tree length, and may be varied by a displaceable bridge. The device for controlling the light beam may be a mirror, which is supported on both the parts of the oscillating device, so that the varying magnetic field causes the mirror to rotate. Alternativ'ely-adiap ragm with one or more serrations may be fixed to each tongue. .1! these diaphragms are placed contiguously to one another they can'be used to' produce a push pull track. 4 The invention is illustrated by the accompanying drawings.

Apparatus having a two-pole electromagnet.

Fig. l is a side elevation of one paratus with parts removed.

' Fig. 2 is a perspective view with the parts separated.

Figures 3, 4, and 5 show perspective views of s diiierent "orms or the mirror.

Figure 6, 7, and 8 are cross-sections of devices showing difierent shaped pole pieces.

Figures 9 and 10 are side views of devices with a pole piece as shown in Figure 8.

Figure 11 is an exploded view of a modifica- "on.

Figure 12 is a perspective view 01' a modified light controlling element. A a

Figure 13a to Figure 13d are diagrams for explaining a method 01 control.

Fig. 14 is a diagram that shows another arrangement of the light control elements Referring to Figures 1 and 2, a permanent magnet I has two pole pieces 2 and 3. 7 Between the magnet I and the pole piece {there are fixed two tongues l which are magnetited by the magnet I. A two-p ole electromagnet is placed on the pole piece 3; the controlling currents flow through the coils 5, i. The free end of each tongue 8 is situated above one pole l of the electromagnet. The coils 5, i are so wound "and connected that when a north pole is produced in one limb a south pole is produced in the other, and vice 'versa. The field of the electromagnet and that of the permanent magnet will together cause one of the tongues I tobe attracted to and the other to be repelled from'the electro-magnet. Thus the free ends of the two tongues move in opposite direc- .tions. A mirror I I is supported by knife edges on ;the ends of both tongues I, and turns as these ends move in opposite directions. This turning is used to control a beam of light'refiected by the mirror. 3

The connection between the mirror and the ends of the tonguescan be of various kinds. It may be directly on the tongues or on a mirror support, the mirror or support having projections, for example knife edges or points, which rest on the tongues. The mirror support preferably rests -in cavities in the pole piece 2.. In Figure 3, for example, a mirror support is shown havingcorners l bent downwards to bear on the tongues, and corners ll bent upwards to fit in cavities in the pole piece 2. Y 1

Figure 4 shows a support Ii for a rectangular mirror II. In all these examples the tongues 8 can be adapted to hold the mirror or mirror support between themselves and the pole piece without the necessity for any further expedient. For

i'orm of alladjusting the distance between the two pole pieces and the tongues a distance piece 4 with a shim l3 adapted to be screwed on to the pole pieces, or a distance screw, can be used. Instead of the arrangement shown in Figure 3 in which the corners l engage in cavities in the pole piece 2, projections H, as shown in Figure 5, may be fixed to the pole piece, and bear on the mirror or mirror support. In this case all points on which the mirror or the mirror support is adapted to turn are in one plane. Thus the points need perform the least necessary movements.

The resonant frequency of the tongues 8 can be adjusted by a bridge [5. The amplitude of the vibrations can be restricted to the desired extent by a suitable piece 16 of damping material.

The pole piece 2 is perforated as at H for passage of the light beam to be controlled.

There should be no appreciable alteration in the reluctance of the circuit for the permanent field as the deflections of the tongues 8 vary. In order to reduce the alteration to a minimum the distance between the pole piece 2 and the tongues 8 is made large compared with that between the tongues and the pole pieces of the electromagnet 1; the variation is further reduced by ensuring that the flux enters the edges of the tongues from the side. This can be procured by proper design of the pole pieces 2, and Figures 6 to show examples of such design.

. In Figure 6 the pole piece 22 is U-shaped, so

' that the permanent field flux enters the edges of the tongues 8 as shown by the lines of force. In Figure '7 the pole piece 23 is T-shaped.

In Figures 8 to 10 the pole piece 24 is shown underneath the tongues 8 and 26 respectively. The lines of force are shown in Figure 8. The part It? serves the purpose of providing a counter-support for the mirror. In Figure 10 the tongues 26 are shown attached not to the magnet l but to the part 3.

In the apparatus described the circuit of the variable flux is solely through parts which can be made of thin sheets of material of suitably high reversible permeability, of which the tongues can also be made. The smaller natural frequency which tongues of such material would have in comparison with a tongue of like dimensions made of steel can be compensated by properly shaping the tongues. It is advantageous for the flux to pass through the tongues transversely to their axis since the cross-section of the bundles of magnetic lines is then larger while their length is reduced to a minimum; further the cross-section of the air-gap is large and it therefore has a small reluctance.

-Figure 11 shows apparatus which is similar to those already described, but in which the bent magnet-I9 takes the place of the magnet-l and pole piece 3, and diaphragms that of the mirror. The whole piece corresponds with element 2 of Figs. 1 and 2. The diaphragms fixed to tongues 21 and 25 may have one or more serrations .and are placed with their adjacent edges contiguous as shown in Figs. 11 and 12 respectively.

With this apparatus it is possible to make a push pull track which can also bearra'nged as a track of diminished ground noise. The method of control is explained by Figures 13a to 13d. Figure 13a shows the. position of rest in which the beam of light-2| is adjusted so that the lower apices of the serrations of the diaphragms 20 lie on the centre line of the beam of light as shown in Figure 13d. Figure 131) shows the maximum deflection of the diaphragms in one direction and Figure 13c that in the opposite direction. It is to be observed that at any given moment only one side of the track is illuminated, while the other side remains dark. If the sound track is to be reproduced on a reversal film, the beam Instead of the diaphragms being arranged to produce the push pull track as described, they may be fixed to the tongues in such a manner that their serrations interpenetrate as shown in Figure 14. In this case the usual 'multi-edge variable width sound track is obtained.

What we claim is:

1. In an apparatus for controlling a beam of light in combination a permanent magnet comprising two pole pieces, two electro-magnets arranged between said pole pieces, each of said electro-magnets having a free end-said electromagnets being traversed by the controlling currents in such a manner that said free ends are oppositely magnetized, two parallel separate tongues adjacent to each other and arranged opposite to said free ends, means for affecting the beam of light carried by said tongues, and means for damping the amplitude of the vibrations of said tongues arranged on said tongues.

2. In an apparatus for controlling a beam of light in combination a permanent magnet comprising two pole pieces, two electro-magnets arranged between said pole pieces, each of said I electro-magnets having a free end, said electro magnets being traversed by the controlling currents in such a manner that said free ends are oppositely magnetized, two parallel separate tongues adjacent to each other and arranged opposite to said free ends, means for affecting the beam of light carried by said tongues, means for damping the amplitude of the vibrations of said tongues arranged on said tongues, and means on said tongues for varying the resonant frequency.

3. In an apparatus for controlling a beam of light in combination a permanent magnet comprising two pole pieces, two electro-magnets arranged between said pole pieces, each of said electro-magnets having a free end, said electromagnets being traversed by the controlling currents in such a manner that said free ends are oppositely magnetized, two parallel separate tongues adjacent to each other and arranged opposite to said free ends, a mirror carried by said tongues, means for damping the amplitudeof the vibrations of said tongues arranged on said tongues, and means on said tongues for varying the resonant frequency.

4. In an apparatus for controlling a beam of light in combination a permanent magnet comprising two pole pieces, two electro-magnets arranged between said pole pieces each of said electro-magnetshaving a free end, said electromagnets being traversed by the controlling currents in such a manner that said free ends are oppositely magnetized, two parallel separate tongues adjacent to each other and arranged opposite to said free ends, each of 'said tongues carry ng a diaphragm with at least one aerration, means for damping the amplitude of the vibrations of said tongues arranged on said tongues, and means on said tongues for varying the resonant frequency.

5. In an apparatus for controlling a beam of light in combination a permanent magnet comprising two pole pieces, two electro-magnets'arranged between said pole pieces, each of said electro-magnets having a free end, said electromagnets being traversed by the controlling currents in such a manner that said'free ends are oppositely magnetized, two parallel separate tongues adjacent to each other and arranged opposite to said free ends; each of said tongues carrying a diaphragm with at least one serration, said diaphragms being placed contiguously to each other, means for damping the amplitudeot the vibrations of said tongues arranged on said tongues, and means on said tongues for varying the resonant frequency.

JOHN EGGERT. HANS FRIEDRICH NISSEN'. 

